Pre-lithiation of electrode materials in a semi-solid electrode

ABSTRACT

Embodiments described herein relate generally to electrochemical cells having pre-lithiated semi-solid electrodes, and particularly to semi-solid electrodes that are pre-lithiated during the mixing of the semi-solid electrode slurry such that a solid-electrolyte interface (SEI) layer is formed in the semi-solid electrode before the electrochemical cell formation. In some embodiments, a semi-solid electrode includes about 20% to about 90% by volume of an active material, about 0% to about 25% by volume of a conductive material, about 10% to about 70% by volume of a liquid electrolyte, and lithium (as lithium metal, a lithium-containing material, and/or a lithium metal equivalent) in an amount sufficient to substantially pre-lithiate the active material. The lithium metal is configured to form a solid-electrolyte interface (SEI) layer on a surface of the active material before an initial charging cycle of an electrochemical cell that includes the semi-solid electrode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. ProvisionalPatent Application Ser. No. 62/074,372, filed Nov. 3, 2014 and titled“Pre-Lithiation of Electrode Materials in a Semi-Solid Electrode,” thedisclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND

As the demand for batteries having better electronic performance, forexample, higher charge capacity, energy density, conductivity, and ratecapabilities increases, new electrode designs are needed to meet thesecriteria Lithium-ion electrodes and particularly anodes suffer fromirreversible capacity loss at the battery formation stage (i.e., theinitial cycling step which includes charging and discharging of theelectrochemical cell). The irreversible capacity loss can happen due tothe transfer of lithium ions from the cathode active material to theanode, where they are used in the formation of the solid-electrolyteinterface (SEI) layer.

SUMMARY

Embodiments described herein relate generally to electrochemical cellshaving pre-lithiated semi-solid electrodes (e.g., anodes), andparticularly to semi-solid electrodes that are pre-lithiated during themixing of the semi-solid electrode slurry such that a solid-electrolyteinterface (SEI) layer is formed in the semi-solid electrode prior to theelectrochemical cell formation and/or initial cycling. In someembodiments, a semi-solid electrode includes about 20% to about 90%/o byvolume of an active material, about 0% to about 25% by volume of aconductive material, about 10% to about 70% by volume of a liquidelectrolyte, and lithium (as lithium metal, a lithium-containingmaterial, and/or a lithium metal equivalent) in an amount sufficient tosubstantially pre-lithiate the active material. The lithium metal isconfigured to form a solid-electrolyte interface (SEI) layer on asurface of the active material and in some cases lithiate and charge theanode material before an initial charging cycle of an electrochemicalcell that includes the semi-solid electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an electrochemical cell accordingto an embodiment.

FIG. 2 is a schematic flow diagram of a method of preparing apre-lithiated anode, according to an embodiment.

FIG. 3 shows an optical image of a copper foil coated with lithium usedto pre-lithiate a semi-solid anode. The semi-solid anode is shown peeledoff from the copper foil after pre-lithiation.

FIG. 4A is a voltage vs capacity profile of a standard electrochemicalcell that includes a standard semi-solid anode, and a pre-lithiatedelectrochemical cell that includes a pre-lithiated semi-solid anode.FIG. 4B is a differential capacitance (dQ/dV) versus charge capacityplot of the standard electrochemical cell and the pre-lithiatedelectrochemical cell.

FIG. 5A is plot of Coulomb efficiency and FIG. 5B is a plot of capacityretained by the second electrochemical cell that includes thepre-lithiated semi-solid anode shown in FIG. 3, after 8 charge anddischarge cycles.

FIG. 6A shows an optical image of a semi-solid anode suspension on whichlithium metal powder is disposed before mixing. FIG. 6B shows thesemi-solid anode suspension after mixing and storing for 1 day.

DETAILED DESCRIPTION

Embodiments described herein relate generally to electrochemical cellshaving pre-lithiated semi-solid electrodes, and particularly tosemi-solid electrodes that are pre-lithiated during the mixing of thesemi-solid electrode slurry such that a solid-electrolyte interface(SEI) layer is formed in the semi-solid electrode before theelectrochemical cell formation. Consumer electronic batteries havegradually increased in energy density with the progress of lithium-ionbattery technology. The stored energy, or charge capacity, of amanufactured battery is a function of: (1) the inherent charge capacityof the active material (mAh/g), (2) the volume of the electrodes (cm³)(i.e., the product of the electrode thickness, electrode area, andnumber of layers (stacks)), and (3) the loading of active material inthe electrode media (e.g., grams of active material per cm³ of electrodemedia). Therefore, to enhance commercial appeal (e.g., increased energydensity and decreased cost), it is generally desirable to increase theareal charge capacity (mAh/cm²) and also to reduce the irreversiblecapacity loss that can occur, particularly in lithium-ion batteries.

Semi-solid electrodes described herein can be made: (i) thicker (e.g.,greater than about 250 μm-up to about 2,000 μm or even greater) due tothe reduced tortuosity and higher electronic conductivity of thesemi-solid electrode, (ii) with higher loadings of active materials, and(iii) with a simplified manufacturing process utilizing less equipment.These semi-solid electrodes can be formed in fixed or flowableconfigurations and decrease the volume, mass and cost contributions ofinactive components with respect to active components, thereby enhancingthe commercial appeal of batteries made with the semi-solid electrodes.The reduced tortuosity and a higher electronic conductivity of thesemi-solid electrodes described herein, results in superior ratecapability and charge capacity of electrochemical cells formed from thesemi-solid electrodes.

Since the semi-solid electrodes described herein can be madesubstantially thicker than conventional electrodes, the ratio of activematerials (i.e., the semi-solid cathode and/or anode) to inactivematerials (i.e. the current collector and separator) can be much higherin a battery formed from electrochemical cell stacks that includesemi-solid electrodes relative to a similar battery formed fromelectrochemical cell stacks that include conventional electrodes. Thissubstantially increases the overall charge capacity and energy densityof a battery that includes the semi-solid electrodes described herein.Examples of electrochemical cells utilizing thick semi-solid electrodesand various formulations thereof are described in U.S. patentapplication Ser. No. 13/872,613 (also referred to as “the '613application”), filed Apr. 29, 2013, entitled “Semi-Solid ElectrodesHaving High Rate Capability,” and U.S. patent application Ser. No.14/202,606 (also referred to as “the '606 application), filed Mar. 10,2014, entitled “Asymmetric Battery, Having a Semi-Solid Cathode and HighEnergy Density Anode,” the entire disclosures of which are incorporatedby reference herein.

Lithium-ion electrodes, and particularly their anodes, can suffer fromirreversible capacity loss at the battery formation stage (i.e., theinitial cycling step which includes charging and discharging of theelectrochemical cell that includes the electrodes). Irreversiblecapacity loss can occur due to consumption of lithium ions from thecathode active material by the anode, which uses those lithium ions inthe formation of the SEI layer. This quantity of consumed lithiumbecomes unavailable for subsequent use in electric charge storage, andtherefore represents an undesirable and irreversible capacity loss.Moreover, this irreversible capacity loss can be accompanied byvolumetric expansion of the anode due to the lithium ions beingirreversibly trapped in the anode material. This volumetric expansionproblem is exacerbated in semi-solid anodes that include high capacityanode materials (e.g., silicon or tin) in the semi-solid anodeformulation, since high capacity anode materials are capable ofincorporating a larger amount of lithium (and enable higher energy celldesigns), as compared with conventional materials such as graphite. Forexample, while graphite can incorporate about 1 lithium atom for every 6carbon atoms, silicon can theoretically incorporate about 4.4 lithiumatoms for every silicon atom. This higher capacity can allow theformation of electrochemical cells with much higher charge capacity perunit area relative to conventional electrochemical cells, however thehigher number of lithium ions incorporated also implies that thesemi-solid anodes that include high capacity materials consume more ofthe lithium from the cathode to form the SEI layer, leading to an evenhigher magnitude of the irreversible capacity. Furthermore, siliconexperiences substantial volumetric expansion due to the incorporation ofthe lithium ions into the silicon atoms. The repeated volume changes(i.e., expansion and/or contraction) can negatively impact the chargecapacity, and cause irreversible mechanical damage which can reduce thelife of the electrochemical cell. Further discussion of the effects oflithiation on stress and morphology of silicon electrodes can be foundin “In situ Measurements of Stress Evolution in Silicon Thin FilmsDuring Electrochemical Lithiation and Delithiation,” by V. Sethuraman,et al., Journal of Power Sources 195 (2010) 5062-5066, the contents ofwhich are hereby incorporated by reference in their entirety.

Embodiments of the semi-solid electrodes described herein arepre-lithiated with lithium during the preparation of the semi-solidelectrode suspension and before formation of an electrochemical cell,thereby overcoming, at least in part, the irreversible capacity loss andvolumetric expansion problems discussed above. The semi-solid electrodesdescribed herein allow the mixing of the lithium metal during the mixingprocess of the electrode slurry, unlike conventional electrodes. This ispossible because the semi-solid electrodes described herein includes theelectrolyte mixed into the semi-solid electrode composition. Theelectrolyte provides a medium for lithium ions provided by the lithiummetal to interact with the active materials included in the semi-solidelectrode, particularly the active materials (e.g., graphite) or highcapacity materials (e.g., silicon or tin) included in a semi-solidanode. This allows the SEI layer to form during the mixing step suchthat when such a pre-lithiated semi-solid anode is paired with a cathodein an electrochemical cell, the lithium ions from the cathode are notused to form the SEI layer. Said another way, because of pre-lithiation,the lithium ions from the cathode do not contribute to irreversiblecapacity loss at the anode, allowing the cathode to maintain its initialcapacity after electrochemical cell formation. Moreover, the electrolyteincluded in the semi-solid electrode composition also protects thelithium metal from the ambient environment (e.g., moisture or humidityof the ambient environment) and thereby, allows the lithium metal toremain stable during the mixing process.

Another advantage provided by pre-lithiation of the semi-solidelectrodes described herein is that the anode can be pre-lithiated suchthat it is completely charged before it is paired with a cathode. Thisenables the use of cathodes that do not include any available lithiumfor forming the SEI layer in the anode. Thus, carbon based anodematerials can be used instead of lithium metal leading to better cyclestability and safety. Furthermore, intercalation of the lithium ionsinto high capacity materials included in the anode can also occur duringthe mixing step, which allows any expansion of the high capacitymaterial to occur during the mixing step. Said another way, thepre-lithiation can pre-expand the semi-solid anode such that thesemi-solid anode experiences less expansion during electrochemical cellformation and subsequent charge/discharge cycles. In this manner, anyphysical damage to the electrochemical cell due to the semi-solid anodeexpansion is substantially reduced or in certain cases possiblyeliminated. Thus, electrochemical cells that include such pre-lithiatedsemi-solid anodes can have substantially higher mechanical stability andlonger life compared to anodes (e.g., semi-solid anodes) that are notpre-lithiated.

Embodiments of the pre-lithiated semi-solid electrodes described hereinprovide several advantages over conventional electrodes including, forexample: (1) formation of SEI layer on an active material of thesemi-solid electrode (e.g., the anode) before the electrochemical cellis formed; (2) limiting or otherwise substantially eliminating theformation of an SEI layer with lithium ions extracted from the otherelectrode (e.g., the cathode); (3) retaining of substantially all of aninitial capacity of the other electrode (e.g., the cathode) afterelectrochemical cell formation; (4) pre-expansion of semi-solid anodesthat include a high capacity material by pre-lithiation beforeelectrochemical cell formation to limit and or reduce any volumetricexpansion of the semi-solid anode on electrochemical cell formation andduring regular use; and (5) enhancing the charge capacity andoperational lifetime of the electrochemical cell.

In some embodiments, a semi-solid electrode includes about 20% to about90% by volume of an active material, about 0% to about 25% by volume ofa conductive material, about 10% to about 70% by volume of a liquidelectrolyte, and lithium (as lithium metal, a lithium-containingmaterial, and/or a lithium metal equivalent) in an amount sufficient tosubstantially pre-lithiate the active material. The lithium isconfigured to form a solid-electrolyte interface (SEI) layer on asurface of the active material before an initial charging cycle of anelectrochemical cell that includes the semi-solid electrode. In someembodiments, the lithium metal can include at least one of lithium metalpowder, lithium salt, lithium foil, and lithium metal disposed on asemi-solid electrode current collector.

In some embodiments, a semi-solid electrode, excluding the electrolytecomponent, includes about 75% to about 100% by weight of an activematerial, about 0% to 50% by weight of a conductive material, and about1% to 50% lithium metal or lithium-ion equivalents. The total solidcomponents of the electrode are composed of the active material,conductive material, and lithium-ion equivalents. The solid componentscompose of 35% to about 90% by volume of the semi-solid electrode andthe electrolyte composes of 10% to about 65% by volume of the semi-solidelectrode. The lithium metal is added to the electrode in order toconsume the irreversible capacity of the anode material, which can rangefrom 1% to 50% of the theoretical first charge capacity of the anodematerial. In other usages, the lithium metal may be mixed with anon-lithiated cathode material to create a cathode material that islithiated for use in a secondary battery such as FeS₂. In this case, theamount of lithium metal or lithium-ion equivalents used would be equalto the total available capacity of the cathode. Another usage ofpre-lithiation is to lithiate the anode to not only consume all theirreversible capacity but also further lithiate the anode in order toprovide a buffer for active lithium-ions that would be saved as areserve in future cycling usage. In such embodiments, the amount oflithium metal used would range from 10% to 50% of the theoreticalcapacity of the anode. In another example, the pre-lithiation processcould be used to lithiate the cathode material to provide it with anexcess amount of lithium ions (i.e., to “over-lithiate” the cathode),thus possibly making the material more stable during electrochemicalcycling.

In some embodiments, a method of preparing a pre-lithiated anodeincludes combining an active material and a lithium metal to form apre-lithiated anode. An electrolyte is combined with the pre-lithiatedmaterial to form a semi-solid anode material. The semi-solid anodematerial is then formed into a semi-solid anode. In some embodiments, aconductive material can optionally be combined with the pre-lithiatedanode material. In some embodiments, a high capacity material canoptionally be combined with the pre-lithiated anode material.

As used herein, the term “about” and “approximately” generally mean plusor minus 100/% of the value stated, e.g., about 250 μm would include 225μm to 275 μm, about 1,000 μm would include 900 μm to 1,100 μm.

As used herein, the term “semi-solid” refers to a material that is amixture of liquid and solid phases, for example, such as particlesuspension, colloidal suspension, emulsion, gel, or micelle.

As used herein, the terms “conductive carbon network” and “networkedcarbon” relate to a general qualitative state of an electrode. Forexample, an electrode with a carbon network (or networked carbon) issuch that the carbon particles within the electrode assume an individualparticle morphology and arrangement with respect to each other thatfacilitates electrical contact and electrical conductivity betweenparticles and through the thickness and length of the electrode.Conversely, the term “unnetworked carbon” relates to an electrodewherein the carbon particles either exist as individual particle islandsor multi-particle agglomerate islands that may not be sufficientlyconnected to provide adequate electrical conduction through theelectrode.

As used herein, the term “electrochemical cell formation” refers to theinitial charge and/or discharge cycle performed on an electrochemicalcell after the components of the electrochemical cell (e.g., cathode,anode, spacer, current collectors, etc.) are assembled for the firsttime to form the electrochemical cell.

As used herein, the term “capacity” may be synonymous with “batterycapacity,” “volumetric energy density,” and/or “specific energy.”

FIG. 1 shows a schematic illustration of an electrochemical cell 100.The electrochemical cell 100 includes a positive current collector 110,a negative current collector 120 and a separator 130 disposed betweenthe positive current collector 110 and the negative current collector120. The positive current collector 110 is spaced from the separator 130by a first distance t₁ and at least partially defines a positiveelectroactive zone. The negative current collector 120 is spaced fromthe separator 130 by a second distance t₂ and at least partially definesa negative electroactive zone. A semi-solid cathode 140 is disposed inthe positive electroactive zone and a semi-solid anode 150 is disposedin the negative electroactive zone. In some embodiments, the thicknessof the positive electroactive zone defined by the distance t₁ and/or thethickness of the negative electroactive zone defined by the distance t₂can be in range of about 250 μm to about 2,000 μm.

The semi-solid cathode 140 and/or the semi-solid anode 150 can bedisposed on a current collector, for example, coated, casted, dropcoated, pressed, roll pressed, or deposited using any other suitablemethod. The semi-solid cathode 140 can be disposed on the positivecurrent collector 110 and the semi-solid anode 150 can be disposed onthe negative current collector 120. For example the semi-solid cathode140 and/or the semi-solid anode 150 can be coated, casted, calenderedand/or pressed on the positive current collector 110 and the negativecurrent collector 120, respectively. The positive current collector 110and the negative current collector 120 can be any current collectorsthat are electronically conductive and are electrochemically inactiveunder the operating conditions of the cell. Typical current collectorsfor lithium cells include copper, aluminum, or titanium for the negativecurrent collector 120 and aluminum for the positive current collector110, in the form of sheets or mesh, or any combination thereof.

Current collector materials can be selected to be stable at theoperating potentials of the semi-solid cathode 140 and the semi-solidanode 150 of the electrochemical cell 100. For example, in non-aqueouslithium systems, the positive current collector 110 can includealuminum, or aluminum coated with conductive material that does notelectrochemically dissolve at operating potentials of 2.5-5.0 V withrespect to Li/Li⁺. Materials coating an aluminum current collector mayinclude platinum, gold, nickel, conductive metal oxides such as vanadiumoxide, and carbon. The negative current collector 120 can include copperor other metals that do not form alloys or intermetallic compounds withlithium, carbon, and/or coatings comprising such materials disposed onanother conductor.

The semi-solid cathode 140 and the semi-solid anode 150 included in anelectrochemical cell can be separated by a separator 130. For example,the separator 130 can be any conventional membrane that is capable ofion transport. In some embodiments, the separator 130 is a liquidimpermeable membrane that permits the transport of ions therethrough,namely a solid or gel ionic conductor. In some embodiments the separator130 is a porous polymer membrane infused with a liquid electrolyte thatallows for the shuttling of ions between the semi-solid cathode 140 andthe semi-solid anode 150 electroactive materials, while preventing thetransfer of electrons. In some embodiments, the separator 130 is amicroporous membrane that prevents particles forming the positive andnegative electrode compositions from crossing the membrane. In someembodiments, the separator 130 is a single or multilayer microporousseparator, optionally with the ability to fuse or “shut down” above acertain temperature so that it no longer transmits working ions, of thetype used in the lithium ion battery industry and well-known to thoseskilled in the art. In some embodiments, the separator 130 can include apolyethyleneoxide (PEO) polymer in which a lithium salt is complexed toprovide lithium conductivity, or Nafion™ membranes which are protonconductors. For example, PEO based electrolytes can be used as theseparator 130, which is pinhole-free and a solid ionic conductor,optionally stabilized with other membranes such as glass fiberseparators as supporting layers. PEO can also be used as a slurrystabilizer, dispersant, etc. in the positive or negative redoxcompositions. PEO is stable in contact with typical alkylcarbonate-based electrolytes. This can be especially useful inphosphate-based cell chemistries with cell potential at the positiveelectrode that is less than about 3.6 V with respect to Li metal. Theoperating temperature of the redox cell can be elevated as necessary toimprove the ionic conductivity of the membrane.

The semi-solid cathode 140 can be a semi-solid stationary cathode. Thesemi-solid cathode 140 can include an ion-storing solid phase materialwhich can include, for example, an active material and/or a conductivematerial. The quantity of the ion-storing solid phase material can be inthe range of about 0% to about 90% by volume. The semi-solid cathode 140can include an active material such as, for example, a lithium bearingcompound (e.g., Lithium Iron Phosphate (LFP), LiCoO₂, LiCoO₂ doped withMg, LiNiO₂, Li(Ni, Co, Al)O₂ (known as “NCA”), Li(Ni, Mn, Co)O₂ (knownas “NMC”), LiMn₂O₄ and its derivatives, etc.). The semi-solid cathode140 can also include a conductive material such as, for example,graphite, carbon powder, pyrolytic carbon, carbon black, carbon fibers,carbon microfibers, carbon nanotubes (CNTs), single walled CNTs, multiwalled CNTs, fullerene carbons including “bucky balls,” graphene sheets,aggregates of graphene sheets, and/or any other conductive material,alloys or combination thereof. The semi-solid cathode 140 can alsoinclude a non-aqueous liquid electrolyte such as, for example, ethylenecarbonate, dimethyl carbonate, diethyl carbonate, propylene carbonate,gamma butyrolactone, or any other electrolyte described herein orcombination thereof. In some embodiments, the electrolyte comprises oneor more of the following salts: lithium hexafluorophosphate (LiPF₆),LiPF₅(CF₃), LiPF₅(C₂F₅), LiPF₅(C₃F₇). LiPF₄(CF₃)₂, LiPF₄(CF₃)(C₂F₅),LiPF₃(CF₃)₃, LiPF₃(CF₂CF₃)₃, LiPF₄(C₂O₄)₂, LiBF₄, LiBF₃(C₂F₅), LiBOB,lithium bis(oxalato)borate (LiBOP), lithium oxalyldifluoroborate(LIODFB), lithium difluoro(oxalato)borate (LiDFOB), lithiumbis(trifluoro methanesulfonyl)imide (LiTFSI), LiN(SO₂CF₃)₂, lithiumbis(fluorosulfonyl)imide (LiFSI), LiN(SO₂F)₂, LiN(SO₂C₂F₅)₂, LiCF₃SO₃,LiAsF₆, LiSbF₆, LiClO₄, LiTFSI, LiFSI, and/or other organic or inorganicanions and/or compounds, for example belonging to the families listedherein.

In some embodiments, the semi-solid anode 150 includes an ion-storingsolid phase material which can include, for example, an active materialand/or a conductive material. The quantity of the ion-storing solidphase material can be in the range of about 0% to about 90% by volume.The anode 150 can include an anode active material such as, for example,lithium metal, carbon, lithium-intercalated carbon, graphite, lithiumnitrides, lithium alloys and lithium alloy forming compounds of silicon,bismuth, boron, gallium, indium, zinc, tin, tin oxide, antimony,aluminum, titanium oxide, molybdenum, germanium, manganese, niobium,vanadium, tantalum, gold, platinum, iron, copper, chromium, nickel,cobalt, zirconium, yttrium, molybdenum oxide, germanium oxide, siliconoxide, silicon carbide, any other materials or alloys thereof, and anyother combination thereof.

The semi-solid anode 150 (e.g., a semi-solid anode) can also include aconductive material which can be a carbonaceous material such as, forexample, graphite, carbon powder, pyrolytic carbon, carbon black, carbonfibers, carbon microfibers, carbon nanotubes (CNTs), single walled CNTs,multi walled CNTs, fullerene carbons including “bucky balls”, graphenesheets and/or aggregate of graphene sheets, any other carbonaceousmaterial or combination thereof. In some embodiments, the semi-solidanode 150 can also include a non-aqueous liquid electrolyte such as, forexample, ethylene carbonate, dimethyl carbonate, diethyl carbonate,propylene carbonate, or any other electrolyte described herein orcombination thereof.

In some embodiments, the semi-solid cathode 140 and/or the semi-solidanode 150 can include active materials and optionally conductivematerials in particulate form suspended in a non-aqueous liquidelectrolyte. In some embodiments, the semi-solid cathode 140 and/or thesemi-solid anode 150 particles (e.g., cathodic or anodic particles,which in some embodiments are secondary particles formed by theagglomeration of primary particles) can have an effective diameter of atleast about 1 μm. In some embodiments, the cathodic or anodic particleshave an effective diameter between about 1 μm and about 10 μm. In otherembodiments, the cathodic or anodic particles have an effective diameterof at least about 10 μm or more. In some embodiments, the cathodic oranodic particles have an effective diameter of less than about 1 μm. Inother embodiments, the cathodic or anodic particles have an effectivediameter of less than about 0.5 μm. In other embodiments, the cathodicor anodic particles have an effective diameter of less than about 0.25μm. In other embodiments, the cathodic or anodic particles have aneffective diameter of less than about 0.1 μm. In other embodiments, thecathodic or anodic particles have an effective diameter of less thanabout 0.05 μm. In other embodiments, the cathodic or anodic particleshave an effective diameter of less than about 0.01 μm.

In some embodiments, the semi-solid cathode 140 includes about 20% toabout 90% by volume of an active material. In some embodiments, thesemi-solid cathode 140 can include about 40% to about 75% by volume,about 50% to about 75% by volume, about 60% to about 75% by volume, orabout 60% to about 90% by volume of an active material.

In some embodiments, the semi-solid cathode 140 can include about 0% toabout 25% by volume of a conductive material. In some embodiments, thesemi-solid cathode 140 can include about 0.5% to about 25% by volume,about 1% to about 6% by volume, about 6% to about 12%, or about 2% toabout 15% by volume of a conductive material.

In some embodiments, the semi-solid cathode 140 can include about 10% toabout 70% by volume of an electrolyte. In some embodiments, thesemi-solid cathode 140 can include about 30% to about 60%, about 40% toabout 50%, or about 10% to about 40% by volume of an electrolyte.

In some embodiments, the semi-solid anode 150 can include about 20% toabout 90% by volume of an active material. In some embodiments, thesemi-solid anode 150 can include about 40% to about 75% by volume, about50% to about 75%, about 60% to about 75%, or about 60% to about 90% byvolume of an active material.

In some embodiments, the semi-solid anode 150 can include about 0% toabout 20% by volume of a conductive material. In some embodiments, thesemi-solid anode 150 can include about 1% to about 10%, 1% to about 6%,about 0.5% to about 2% by volume, about 2% to about 6%, or about 2% toabout 4% by volume of a conductive material.

In some embodiments, the semi-solid anode 150 can include about 10%/o toabout 70% by volume of an electrolyte. In some embodiments, thesemi-solid anode 150 can include about 30% to about 60%, about 40% toabout 50%, or about 10% to about 40% by volume of an electrolyte.

Examples of active materials, conductive materials, and/or electrolytesthat can be used in the semi-solid cathode 140 and/or the semi-solidanode 150 compositions, various formulations thereof, andelectrochemical cells formed therefrom, are described in the '613application and the '606 application.

In some embodiments, the semi-solid anode 150 can also include about 1%to about 30% by volume of a high capacity material. Such high capacitymaterials can include, for example, silicon, bismuth, boron, gallium,indium, zinc, tin, antimony, aluminum, titanium oxide, molybdenum,germanium, manganese, niobium, vanadium, tantalum, iron, copper, gold,platinum, chromium, nickel, cobalt, zirconium, yttrium, molybdenumoxide, germanium oxide, silicon oxide, silicon carbide, any other highcapacity materials or alloys thereof, and any combination thereof. Insome embodiments, the semi-solid anode can include about 1% to about 5%by volume, about 1% to about 10% by volume, or about 1% to about 20% byvolume of the high capacity material. In some embodiments, the highcapacity material can constitute up to 50% of the volume of thesemi-solid anode. In other embodiments, the high capacity material canconstitute up to 100%, or substantially all, of the volume of thesemi-solid anode. Examples of high capacity materials that can beincluded in the semi-solid anode 150, various formulations thereof andelectrochemical cells formed therefrom, are described in the '606application.

The semi-solid anode 150 and/or the semi-solid cathode 140 can alsoinclude a lithium metal, a lithium-containing material (e.g., LiFePO₄,Li(Mn_(1/3), Ni_(1/3)Co_(1/3))O₂ and LiMn₂O₄, and/or LiCoO₂), and/or alithium metal equivalent (e.g., a lithium ion, which may or may not beintercalated and/or associated with an electrode material) in thesemi-solid electrode composition. In some embodiments, the lithium metalcan be included/introduced in the semi-solid anode 150 and/or thesemi-solid cathode 140 during the mixing of the semi-solid electrodesuspension. The lithium metal, lithium-containing material, and/orlithium metal equivalent can be present within the semi-solid anodeand/or the semi-solid cathode in an amount that is sufficient to atleast partially (or, in some embodiments, substantially fully)“pre-lithiate” the semi-solid anode and/or semi-solid cathode. Forexample, the lithium metal, lithium-containing material, and/or lithiummetal equivalent can be included in the semi-solid anode 150 and/orsemi-solid cathode 140 before the electrochemical cell 100 is assembledand formed. The lithium metal, lithium-containing material, and/orlithium metal equivalent can be configured to form an SEI layer on asurface of the active material included in the semi-solid electrode(e.g., the semi-solid anode 150) before an initial charging cycle of theelectrochemical cell 100 (i.e., before electrochemical cell formation).Thus, little or no amount of lithium from the semi-solid cathode 140 isconsumed in forming the SEI layer on the surface(s) of the semi-solidanode active material during the electrochemical cell 100 formationstage. Therefore, the possibility of loss in capacity of the semi-solidcathode 140 due to consumption of cathodic lithium ions in the anodicSEI layer formation is reduced or eliminated.

In some embodiments, the amount of lithium metal, lithium-containingmaterial, and/or lithium metal equivalent may be sufficient to fullycompensate for (i.e., prevent) the traditional lithium consumption thatoccurs in the formation of an SEI layer during initial cell cycling(e.g., lithium ions that are “robbed” from the cathode). In otherembodiments, the amount of lithium metal, lithium-containing material,and/or lithium metal equivalent may exceed the amount required to fullycompensate for the traditional SEI layer formation. In such embodiments,the excess lithium contained within the anode may help to offsetcapacity degradation due to side reactions occurring in the anode,and/or may constitute a “pre-charging” of the anode itself. The amountof pre-charging of the anode, by virtue of excess intercalated lithium(e.g., metallic Li or a compound or ion thereof), depends upon theamount of lithium metal, lithium-containing material, and/or lithiummetal equivalent added. As a result, it is theoretically possible toachieve or exceed a “fully charged” anode state of the anode throughpre-lithiation alone. As illustrated in Tables 1 through 6 (discussedbelow), the required amount of lithium (e.g., as provided in the form oflithium metal, lithium-containing material, and/or lithium metalequivalent) may be calculated by taking into account several factors.These factors may include, depending upon the embodiment, the capacity(e.g., charge capacity) of one or more active materials, the weight ofone or more active materials, the percentage(s) of the capacity of oneor more active materials that is irreversible, the weight and type ofone or more additives, the irreversible capacity of the one or moreadditives, the capacity of lithium (e.g., lithium metal,lithium-containing material, and/or lithium metal equivalent), theoverall capacity of the electrode, and the amount of additional (i.e.,“buffer”) capacity desired.

The amount of lithium metal included in the semi-solid anode 150 candepend on the active material included in the semi-solid anode 150. Forexample, in semi-solid anodes 150 that include graphite as the activematerial, the loss due to SEI layer formation is manifested essentiallyas an irreversible capacity loss during the first cycle (i.e.,electrochemical cell formation) of the electrochemical cell 100. Theadded lithium metal can itself form an SEI contact with the electrolyte,which constitutes an additional irreversible loss. Therefore, the amountof lithium metal added to the semi-solid anode 150 can be directlyrelated to the first cycle irreversible capacity loss of theelectrochemical cell 100. Generally, in graphite anodes, theirreversible capacity loss can be about 5% to about 30% of the initialcapacity of the anode. The amount of lithium metal that can be includedin anodes that include graphite as the active material (e.g., graphitesemi-solid anodes or any other anode that includes graphite) can becalculated as follows. Given that Faraday's constant is 96,500 C/mole,the formula weight of graphite is 12 grams per mole (i.e., a “6-C” ringhas a molecular weight of ˜72 g/mole), and its density is 2.2 grams percm³, the theoretical capacity of graphite is 372 mAh/g forpre-lithiation (for composition LiC₆), and the theoretical volumetriccapacity is 818 mAh/cm³. The calculation of the theoretical capacity ofgraphite (for LiC₆) is as follows:

Molecular  weight  of  LiC₆:  79  g/gmole  (Each  Li  takes  one  6-C  ring)${\frac{1\; {gmole}\mspace{14mu} {Li}^{+}\mspace{14mu} {released}}{1\; {gmole}\mspace{14mu} {LiC}_{6}}\frac{1\; {gmole}\mspace{14mu} {LiC}_{6}}{72\mspace{14mu} g\mspace{14mu} C}\frac{96500{coul}}{1\; {gmole}\mspace{14mu} {Li}^{+}\mspace{14mu} {released}}\frac{\sec \mspace{14mu} {Amp}}{1{{coul}.}}\frac{1{hr}}{3600\sec}\frac{1000\mspace{14mu} {mhr}}{1{hr}}} = {372\frac{{mA}\; {hr}}{g\mspace{14mu} C}}$

Lithium metal has a formula weight of 6.94 grams per mole and a densityof 0.5 grams per cm³. The theoretical capacity of lithium metal is about3,839 mAh/g, and its theoretical volumetric capacity is 1,915 grams percm³. Similar calculations can be performed for other commonly usedactive materials in anodes such as, for example, glassy carbon. In someembodiments, the amount of lithium metal included in the semi-solidanode 150 that includes graphite as an active material, can be in therange of about 1% to about 20% by volume. The lithium metal added to thesemi-solid anode 150 and/or the semi-solid cathode 140 can alsopartially lithiate the semi-solid anode 150 and/or the semi-solidcathode. In such embodiments, during use of the electrochemical cell100, the limiting concentrations of lithium in the charged anddischarged state of the semi-solid anode 150 and/or the semi-solidcathode 140 can have a positive impact on the electrochemical cellvoltage, capacity, life or other electronic properties.

In some embodiments in which the semi-solid anode 150 includes a highcapacity material (e.g., silicon, tin or any other high capacitymaterial described herein), the degree of lithiation should maintain thematerial in an operating range over which the least amount of volumechange occurs. In the case of silicon, this would be somewhere in therange of 10%-80% lithiation. This can extend the life of the semi-solidanode 150 during charge/discharge cycling by limiting the expansion orcontraction of the semi-solid anode 150. This is because thepre-lithiation of the semi-solid anode 150 allows the lithium to beintercalated into the high capacity material (e.g., silicon) beforeelectrochemical cell formation. See “In situ Measurements of StressEvolution in Silicon Thin Films During Electrochemical Lithiation andDelithiation,” by V. Sethuraman, et al., Journal of Power Sources 195(2010) 5062-5066, referenced above. The lithium in the pre-lithiatedsemi-solid anode 150 permanently shifts the lithium concentration rangeover which the anode is cycled, and increases the minimum lithiumconcentration in the semi-solid anode 150 at the end of the discharge(i.e., the semi-solid anode remains substantially lithiated throughoutthe charging and discharging of the cell before, during and after theelectrochemical cell 100 formation). Therefore, in semi-solid anodesthat include a high capacity material, the amount of lithium metal to beadded for effective pre-lithiation can be determined by the optimumcycling range for the semi-solid anode 150 and can be calculated in asimilar fashion as described herein with respect to graphite. Forexample, silicon has a formula weight of 29 grams per mole and densityof 2.33 grams per cm³ and can be pre-lithiated to a composition as highas Li_(4.4)Si. At this composition, the theoretical capacity of thepre-lithiated silicon is 4,212 mAh/g, and the corresponding theoreticalvolumetric capacity is 9,814 mAh-cm³, which is based on the mass andvolume of the starting silicon. Semi-solid anodes of the presentdisclosure that include high-capacity materials (e.g., silicon) maytherefore be formulated to include sufficient lithium (i.e., at the“pre-lithiation stage”) to minimize volume changes during cycling.

Since the lithium metal added to the semi-solid anode 150 that includesa high capacity material can be used to form the SEI layer as well asfor partial lithiation of the anode, the amount of pre-lithiation can bedetermined based on the amount of active material present in thesemi-solid anode 150. For example, in a semi-solid anode 150 thatincludes a high capacity material and inactive material but no activematerial, the amount of lithium added in the pre-lithiation will be usedonly to pre-lithiate the high capacity material (e.g., intercalate inthe high capacity material). By contrast, in a semi-solid anode 150 thatincludes an active material, silicon as a high capacity material, and aninactive material, the amount of lithium added in the pre-lithiationwill be utilized by the active material (e.g., in forming the SEI layer)as well as by the high capacity material (e.g., intercalation of thehigh capacity material). In addition, for a semi-solid anode that haslarge volume changes during cycling, additional loss of working lithiummay be incurred during cycling as fracture of particles and/oraggregates of particles exposes new surface area to the electrolyte, andnew SEI layer(s) can form on such surfaces.

Any suitable form of lithium metal can be included in the semi-solidanode 150 and/or the semi-solid cathode 140 for pre-lithiation. Forexample, the lithium metal can include lithium metal powder, lithiumsalt, and/or lithium foil. Furthermore, the lithium metal can have anyshape or size such as, for example, powder, microparticles,nanoparticles, pieces, foil, etc. In some embodiments, lithium metal canbe first deposited on a metal foil (e.g., a copper foil or an aluminumfoil) or electrode. The semi-solid anode 150 and/or the semi-solidcathode 140 can be disposed on the metal foil or other electrodematerial and can be pre-lithiated from the metal foil or otherwiseelectrode by diffusion or electroplating before assembling theelectrochemical cell 100.

The lithium metal used for pre-lithiation can be mixed in with thesemi-solid anode 150 and/or semi-solid cathode 140 suspension duringpreparation of the suspensions. The lithium metal can have one or morecoatings or treatments to protect it from the ambient environment suchthat the lithium metal does not react with ambient moisture during themixing process. For example, the lithium metal can be treated with CO₂or coated with Al—Li to protect the lithium metal from reacting with theenvironment. Once mixed, the electrolyte included in the semi-solidanode 150 and the semi-solid cathode 140 formulations can protect thelithium metal from reacting with the environment. In some embodiments,the coating on the lithium metal can be formulated to dissolve in theelectrolyte such that lithium metal can interact with the components ofthe semi-solid anode 150 and/or the semi-solid cathode (e.g., form anSEI layer on the active material of the semi-solid anode 150).

In some embodiments, semi-solid anode 150 and semi-solid cathode 140suspensions described herein can be mixed in a batch process, forexample, with a batch mixer that can include, for example, a high shearmixture, a planetary mixture, a centrifugal planetary mixture, a sigmamixture, a CAM mixture, and/or a roller mixture, with a specific spatialand/or temporal ordering of component addition. In some embodiments, asemi-solid anode 150 and/or semi-solid cathode 140 suspension can bemixed in a continuous process (e.g. in an extruder), with a specificspatial and/or temporal ordering of component addition. Once the slurrycomponents have been properly mixed, solid particles, for example, ionconductive polymers, can be further mixed with the semi-solid electrodeslurry. In some embodiments, the slurry mixing can be performed at a lowtemperature, for example, lower than about 25 degrees Celsius (e.g.,about 5 degrees Celsius). Once the semi-solid anode 150 and/orsemi-solid cathode 140 suspensions have been cast into the semi-solidelectrode, the temperature can be allowed to increase, for example, togreater than about 37 degrees Celsius. In some embodiments, mixing canbe performed in a vacuum, in a moisture free environment, and/or in aninert gas atmosphere (e.g., under N₂ or Argon).

The mixing and forming of the components of the semi-solid cathode 140and the semi-solid anode 150 suspensions generally includes: (i) rawmaterial conveyance and/or feeding, (ii) mixing, (iii) mixed slurryconveyance, (iv) dispensing and/or extruding, and (v) forming. In someembodiments, multiple steps in the process can be performed at the sametime and/or with the same piece of equipment. For example, the mixingand conveyance of the slurry can be performed at the same time with anextruder. Each step in the process can include one or more possibleembodiments of that step. For example, each step in the process can beperformed manually or by any of a variety of process equipment. Eachstep can also include one or more sub-processes and, optionally, aninspection step to monitor process quality.

In some embodiments, an anode according to the disclosure is mixed anddispensed via standard methods. A stabilized lithium metal powder isweighed such that the total mass of lithium (excluding inactivestabilizing coating) has the equivalent capacity to the targetpre-lithiation capacity. The lithium powder is selected such that theaverage diameter of a particle is at least one order of magnitudesmaller than the target height of the anode electrode. The powder isdispersed such that it uniformly covers the top of the anode electrode.Afterwards a separator is applied with a slight pressure to the top ofthe electrode, and a cathode electrode is placed on top of the separatorto create a unit cell.

In some embodiments, the process conditions can be selected to produce aprepared semi-solid cathode 140 and/or semi-solid anode 150 suspensionshaving a mixing index of at least about 0.80, at least about 0.90, atleast about 0.95, or at least about 0.975. In some embodiments, theprocess conditions can be selected to produce a semi-solid cathode 140and/or semi-solid anode 150 suspension having an electronic conductivityof at least about 10⁻⁶ S/cm, at least about 10⁻⁵ S/cm, at least about10⁻⁴ S/cm, at least about 10⁻³ S/cm, at least about 10⁻² S/cm, at leastabout 10⁻¹ S/cm, at least about 1 S/cm, or at least about 10 S/cm Insome embodiments, the process conditions can be selected to produce asemi-solid cathode 150 and/or semi-solid anode 140 suspension having anapparent viscosity at room temperature of less than about 100,000 Pa-s,less than about 10,000 Pa-s, or less than about 1,000 Pa-s, all at anapparent shear rate of 1,000 s⁻¹. In some embodiments, the processconditions can be selected to produce a semi-solid cathode 140 and/orsemi-solid anode 150 suspension having two or more properties asdescribed herein. Examples of systems and methods that can be used forpreparing the semi-solid electrode compositions described herein aredescribed in U.S. patent application Ser. No. 13/832,861 (also referredto as “the '861 application”), filed Mar. 15, 2013, entitled“Electrochemical Slurry Compositions and Methods for Preparing theSame,” the entire disclosure of which is incorporated by referenceherein.

FIG. 2 is a schematic illustration of a method 200 for preparing apre-lithiated semi-solid anode, for example, the semi-solid anode 150 orany other semi-solid anode described herein. The method 200 includescombining an active material and a lithium metal to form a pre-lithiatedanode material, at 202. The active material can include any activematerial described with respect to the semi-solid anode 150, forexample, graphite. The lithium metal can be in any form such as, forexample, lithium metal powder, lithium salt, or lithium foil.Furthermore, the lithium metal can have any shape or size such as, forexample, powder, microparticles, nanoparticles, pieces, foil, etc. Insome embodiments, the lithium metal can be deposited on the surface ofthe active material. For example, microparticles or nanoparticles of thelithium metal can be deposited on the surface of the active material(e.g., graphite). In some embodiments, the lithium metal mixed withactive material can be in liquid form. For example, the lithium metalcan be in a molten state, or dissolved in an appropriate solvent to forma solution which can be mixed with the active material. In someembodiments, the lithium metal can have one or more coatings ortreatments to protect it from the ambient environment such that thelithium metal does not react with ambient moisture during the mixingprocess. For example, the lithium metal can be treated with CO₂ orcoated with Al—Li to protect the lithium metal from reacting with theenvironment. The thickness of the coating can be controlled to reducereactivity of the lithium metal. Moreover, in some embodiments, thecoating on the lithium metal can be formulated to dissolve in anelectrolyte included in the semi-solid anode formulation, as describedherein, such that lithium metal can interact with the components of thesemi-solid anode, i.e., the active material. Combining the lithium metalwith the active material can allow the lithium metal to form an SEIlayer on a surface of the active material, as described herein.

In some embodiments, a conductive material can be combined with thepre-lithiated anode material, at 204. The conductive material caninclude carbon powder, CNTs or any other conductive material describedwith respect to the semi-solid anode 150.

In some embodiments, a high capacity material can also be combined withthe pre-lithiated anode material, at 206. The high capacity material caninclude silicon, tin or any other high capacity material described withrespect to the semi-solid anode 150. The lithium metal included in thepre-lithiated anode can also form an SEI layer on the high capacitymaterial (e.g., silicon). Furthermore, the ions of the lithium metal canintercalate into the high capacity material, thereby urging the highcapacity material to expand. In some embodiments, the lithium metal canbe combined with a small portion of the total quantity of an activematerial and/or the high capacity material included in the semi-solidanode, and mixed such that a SEI layer forms over the portion of theactive material and the high capacity material. Once the SEI layer isformed, the remaining active material and/or high capacity material canbe combined with the pre-lithiated portion of the active material and/orthe high capacity material.

An electrolyte is combined with the pre-lithiated anode material to forma semi-solid anode material, at 208. The electrolyte can include anysuitable electrolyte, for example, any electrolyte described withrespect to the semi-solid anode 150. The electrolyte can, for example,enable formation of the semi-solid anode suspension as well as shortcircuit the active material, conductive material, and/or high capacitymaterial included in the semi-solid anode reducing tortuosity andimpedance of the semi-solid anode. Furthermore, the electrolyte candissolve any protective coating on the lithium metal and also facilitatethe formation of the SEI layer by short circuiting the lithium metalwith the active material and/or the high capacity material.

The semi-solid anode material is then formed into a semi-solid anode, at210. For example, the semi-solid anode material can be casted, dropcoated, or formed into the semi-solid anode using any suitable methoddescribed with respect to the semi-solid anode 150. The formedsemi-solid anode can be paired with a cathode, for example, a semi-solidcathode (e.g., the semi-solid cathode 140) and included in anelectrochemical cell, for example, the electrochemical cell 100. Sincethe pre-lithiated semi-solid anode formed using the method 200 alreadyhas the SEI layer formed over the active material, little or no amountof lithium is consumed from the cathode for forming the SEI layer duringthe electrochemical cell formation. Thus, the cathode can retainsubstantially all of its initial capacity (i.e., capacity beforeelectrochemical cell formation) after the electrochemical cell formationprocess. Furthermore, if the pre-lithiated semi-solid anode formed usingthe method 200 includes a high capacity material, the lithium metal isalready intercalated into the high capacity material such that the highcapacity material, and thereby the pre-lithiated semi-solid anode, arepre-expanded. Thus, the pre-lithiated anode experiences only anegligible amount of expansion during the electrochemical cell formationprocess. This can substantially reduce any mechanical damage to thesemi-solid anode due to the expansion, prevent reduction in voltageand/or capacity of the cell (e.g., cracking of the electrode and/or“capacity fade”), and enhance the performance and operational life ofthe pre-lithiated semi-solid anode and thereby, of the electrochemicalcell.

The following examples show pre-lithiated anodes and electronicperformance of pre-lithiated anodes prepared using the methods describedherein. These examples are only for illustrative purposes and are notintended to limit the scope of the present disclosure.

Example 1: Pre-Lithiation of Semi-Solid Anode Using Lithium CoatedCopper Foil

In this example, a semi-solid anode was pre-lithiated using a lithiumcoated copper foil. A semi-solid anode was prepared by mixing about50%/o by volume of mesophase graphite powder (MGP-A from China SteelChemical Corporation) as the active material, with about 2% by volume ofcarbon black (C45 obtained from Timcal) as the conductive material, andabout 48% by volume of an electrolyte. The electrode included ethylenecarbonate (EC) and gamma butyrolactone (GBL) in a 30:70 ratio, about 1.1moles of LiBF₄, about 2% by weight of vinylene carbonate (VC), about1.5% by weight of LiBOB, and about 0.5% by weight of tris (2-ethylhexyl)phosphate (TOP). The semi-solid anode components were mixed in aRESODYN® mixer for about 12 mins. The semi-solid anode was disposed ontwo sides of a lithium metal coated copper foil which also serves as thenegative current collector. The semi-solid anode was paired with asemi-solid cathode. The semi-solid cathode included about 50% by volumeof LFP as the active material, about 0.8% by volume of Ketjen black asthe conductive material, and about 49.2% by volume of an electrolyte,which was same the electrolyte used to prepare the semi-solid anodesuspension. The components of the semi-solid cathode were mixed in aspeed mixer at about 1,250 rpm for about 90 seconds. The semi-solidcathode was disposed on one side of a current collector and paired withthe semi-solid anode, with a spacer disposed therebetween to prepare apre-lithiated electrochemical cell. Since the anode was disposed on bothsides of the lithium coated copper foil, two cathodes were prepared andpaired with the semi-solid anode disposed on each side of the lithiumcoated copper foil. The pre-lithiated electrochemical cell was disposedin a vacuum seal pouch and kept under dry conditions for 3 days to allowthe lithium metal disposed on the lithium coated copper foil topre-lithiate the anode.

FIG. 3 shows a test semi-solid anode, prepared using the same process asthe semi-solid anode described herein, peeled off from a lithium metalcoated copper foil after three days of storage in a vacuum sealed pouch.The portion of the lithium metal coated copper foil on which the testsemi-solid anode was disposed is devoid of any lithium after the anodeis peeled off such that the underlying copper can be seen. This showsthat the lithium metal disposed on the portion of the copper foil incontact with the test semi-solid anode diffused and/or reacted with thegraphite included in the test semi-solid anode and possibly formed anSEI layer on the graphite thus, pre-lithiating the semi-solid anode.

A standard electrochemical cell was prepared in exactly the same manneras the pre-lithiated electrochemical cell except that the negativecurrent collector included a bare copper foil not coated with thelithium metal. Thus, the semi-solid anode of the standardelectrochemical cell was not pre-lithiated.

The pre-lithiated electrochemical cell which included the pre-lithiatedsemi-solid anode was subjected to electrochemical tests to determine theelectronic performance of the electrochemical cell. The electrochemicalwas subjected to 2 cycles at a C-Rate of C/10 and 10 cycles at a C-rateof C/4. All testing was performed using a MACCOR® battery tester.

FIG. 4A shows a plot of voltage vs capacity of the pre-lithiatedelectrochemical cell and the standard electrochemical cell after onecharge/discharge cycle, and FIG. 4B shows a plot of differentialcapacity (dQ/dV) vs capacity of the pre-lithiated and standardelectrochemical cells, derived from FIG. 4A. The Coulomb efficiency ofthe pre-lithiated electrochemical cell was about 96.6%, and the Coulombefficiency of the standard electrochemical cell was about 88.2%. As canbe seen in FIGS. 4A and 4B, the pre-lithiated electrochemical cellcharges substantially faster compared to the standard electrochemicalcell. While the final capacity retained by the pre-lithiatedelectrochemical cell is slightly lower than the standard electrochemicalcell, this is attributed to lower cell quality and data variation. Oneexplanation can be that since the semi-solid anode is disposed on thelithium coated copper current collector and a portion of the lithium incontact with the semi-solid anode intercalates with the semi-solid anodematerial to pre-lithiate the semi-solid anode, the copper foil disposedbelow the lithium metal contacts the pre-lithiated semi-solid anode.This contact can however, be of poor quality which can increaseimpedance and reduce overall charge capacity of the pre-lithiatedelectrochemical cell prepared using the lithium coated copper foilmethod.

FIG. 5A shows a plot of Coulomb efficiency of the pre-lithiatedelectrochemical cell after 8 cycles, while FIG. 5B shows a plot ofcapacity retained by the pre-lithiated electrochemical cell after 8cycles. The pre-lithiated electrochemical cell retained about 96% of itsinitial Coulomb efficiency, and retains about 72% of its initialcapacity after 8 cycles. This again is attributed to the low quality ofthe pre-lithiated electrochemical cell because of the low quality of theelectronic contact between the pre-lithiated semi-solid anode with thecopper foil negative current collector after the lithium metal coatingreacts with the semi-solid anode active material and is incorporatedinto the semi-solid anode.

Example 2: Pre-Lithiation by Mixing Lithium Powder in Semi-Solid AnodeSuspension

In this example, a lithium powder was incorporated into a semi-solidanode during the preparation of the semi-solid anode suspension topre-lithiate the anode. A semi-solid anode suspension was preparedsimilar to the semi-solid anode described in Example 1. The semi-solidanode was mixed with lithium powder and stored for 1 day. The quantityof the lithium powder mixed with the semi-solid anode suspension wassuch that the capacity of the lithium powder was about 15% of the totalcharge capacity (including that of the graphite) included in thesemi-solid anode. FIG. 6A shows an optical image of the semi-solid anodewith the lithium powder added but not mixed into the semi-solid anodesuspension. The semi-solid anode suspension appeared wet showing thatlithium metal has not reacted with the semi-solid anode active material,i.e., graphite. FIG. 6B shows the semi-solid anode suspension aftermixing and storing for 1 day. The semi-solid anode suspension appeareddry after 1 day which indicated that the lithium had reacted with thegraphite, possibly forming an SEI layer on the graphite.

Tables 1-6 below contain exemplary electrode component parametersaccording to some embodiments of the disclosure, as well as calculationsof the theoretical percentage of lithium present in a prelithiatedsemi-solid anode prior to the application of current under variousscenarios. Table 1 shows exemplary parameters and calculations for ananode formulation in which a single active material (mesophase graphitepowder (MGP-A)) is used, and in which the lithium content is sufficientfor fully “pre-lithiating” (i.e., compensating for the traditional SEIformation) without any additional “buffer” or extra capacity by way ofexcess intercalated lithium. Table 2 shows exemplary parameters andcalculations for an anode formulation in which a single active material(MGP-A) is used, and in which the lithium percentage is calculated toinclude a 5% buffer (i.e., the graphite is ˜5% charged prior to cellassembly and/or cycling). Tables 3 and 4 include parameters andcalculations similar to those in Table 2, but are directed to bufferpercentages of 50% and 100%, respectively. Table 5 shows exemplaryparameters and calculations for an anode formulation in which two activematerials (MGP-A and soft carbon) are used, and in which the lithiumpercentage is calculated to include a 5% buffer. Table 6 shows exemplaryparameters and calculations for an anode formulation in which two activematerials (MGP-A and silicon, a high-capacity material) are used, and inwhich the lithium percentage is calculated to include a 5% buffer.

TABLE 1 One Active Material, Na Buffer Total electrode weight 1 g ActiveMaterial 1 = mesophase graphite powder (MGP-A) 50% by volume Carbonadditive = carbon black 2% by volume Electrolyte 48% by volumeElectrolyte composition ethylene carbonate (EC) 30:00:00 ratio gammabutyrolactone (GBL) 70:00:00 LiBF4 1.1 moles vinylene carbonate (VC) 2%by weight LiBOB 1.5% by weight Tris (2-ethylhexyl) phosphate (TOP) 0.5%by weight Density Active Material 1 = mesophase graphite powder (MGP-A)2.27 g/cc Carbon additive = carbon black 1.9 g/cc Electrolyte 1.26 g/ccActive Material 1 = mesophase graphite powder (MGP-A) 63.84% by weightCarbon additive = carbon black 2.14% by weight Electrolyte 34.02% byweight Weight g1: Active Material 1 = mesophase graphite powder (MGP-A)0.639 g c: Carbon additive = carbon black 0.021 g e: Electrolyte 0.340 ga1: Capacity of Active Material 1 (mesophase graphite): 360 mAh/g (<--@0.1 C) x1: Estimated % of a1 that is irreversible:   10% y:Irreversible capacity of carbon additive 200 mAh/g b: Capacity oflithium metal 3860 mAh/g d: (a1 * g1 * x1 + a2 * g2 * x2 + . . . an *gn * xn)/b d = 0.00595 g % w = d/(g + d + c + e) = % lithium present inthe perlithiated semi-solid anode prior to the application of current %w = 0.592%

TABLE 2 One Active Material, 5% Buffer Total electrode weight 1 g ActiveMaterial 1 = mesophase graphite powder (MGP-A) 50% by volume Carbonadditive = carbon black 2% by volume Electrolyte 48% by volumeElectrolyte composition ethylene carbonate (EC) 30:00:00 ratio gammabutyrolactone (GBL) 70:00:00 LiBF4 1.1 moles vinylene carbonate (VC) 2%by weight LiBOB 1.5% by weight Tris (2-ethylhexyl) phosphate (TOP) 0.5%by weight Density Active Material 1 = mesophase graphite powder (MGP-A)2.27 g/cc Carbon additive = carbon black 1.9 g/cc Electrolyte 1.26 g/ccActive Material 1 = mesophase graphite powder (MGP-A) 63.84% by weightCarbon additive = carbon black 2.14% by weight Electrolyte 34.02% byweight Weight g1: Active Material 1 = mesophase graphite powder (MGP-A)0.638 g c: Carbon additive = carbon black 0.021 g e: Electrolyte 0.340 ga1: Capacity of Active Material 1 (mesophase graphite): 360 mAh/g (<--@0.1 C) x1: Estimated % of a1 that is irreversible:   10% b: Capacity oflithium metal 3860 mAh/g z: Extra (for improving cycle life) 5% <--buffer y: Irreversible capacity of carbon additive 200 mAh/g h: Capacityof electrode 206.85116 mAh d: (a1 * g1 * x1 + a2 * g2 * x2 + . . . an *gn * xn + c * y + h * z)/b d = 0.00974 g % w = d/(g + d + c + e) = %lithium present in the prelithiated semi-solid anode prior to theapplication of current % w = 0.965%

TABLE 3 One Active Material, 50% Buffer Total electrode weight 1 gActive Material 1 = mesophase graphite powder (MGP-A) 50% by volumeCarbon additive = carbon black 2% by volume Electrolyte 48% by volumeElectrolyte composition ethylene carbonate (EC) 30:00:00 ratio gammabutyrolactone (GBL) 70:00:00 LiBF4 1.1 moles vinylene carbonate (VC) 2%by weight LiBOB 1.5% by weight Tris (2-ethylhexyl) phosphate (TOP) 0.5%by weight Density Active Material 1 = mesophase graphite powder (MGP-A)2.27 g/cc Carbon additive = carbon black 1.9 g/cc Electrolyte 1.26 g/ccActive Material 1 = mesophase graphite powder (MGP-A) 63.84% by weightCarbon additive = carbon black 2.14% by weight Electrolyte 34.02% byweight Weight g1: Active Material 1 = mesophase graphite powder (MGP-A)0.638 g c: Carbon additive = carbon black 0.021 g e: Electrolyte 0.340 ga1: Capacity of Active Material 1 (mesophase graphite): 360 mAh/g (<--@0.1 C) x1: Estimated % of a1 that is irreversible: 10% b: Capacity oflithium metal 3860 mAh/g z: Extra (for improving cycle life) 50% <--buffer y: Irreversible capacity of carbon additive 200 mAh/g h: Capacityof electrode 206.8512 mAh d: (a1 * g1 * x1 + a2 * g2 * x2 + . . . an *gn * xn + c * y + h * z)/b d = 0.03386 g % w = d/(g + d + c + e) = %lithium present in the prelithiated semi-solid anode prior to theapplication of current % w = 3.275%

TABLE 4 One Active Material, 100% Buffer Total electrode weight 1 gActive Material 1 = mesophase graphite powder (MGP-A) 50% by volumeCarbon additive = carbon black 2% by volume Electrolyte 48% by volumeElectrolyte composition ethylene carbonate (EC) 30:00:00 ratio gammabutyrolactone (GBL) 70:00:00 LiBF4 1.1 moles vinylene carbonate (VC) 2%by weight LiBOB 1.5% by weight Tris (2-ethylhexyl) phosphate (TOP) 0.5%by weight Density Active Material 1 = mesophase graphite powder (MGP-A)2.27 g/cc Carbon additive = carbon black 1.26 g/cc Electrolyte 1.26 g/ccActive Material 1 = mesophase graphite powder (MGP-A) 63.84% by weightCarbon additive = carbon black 2.14% by weight Electrolyte 34.02% byweight Weight g1: Active Material 1 = mesophase graphite powder (MGP-A)0.638 g c: Carbon additive = carbon black 0.021 g e: Electrolyte 0.340 ga1: Capacity of Active Material 1 (mesophase graphite): 360 mAh/g (<--@0.1 C) x1: Estimated % of a1 that is irreversible:   10% b: Capacity oflithium metal 3860 mAh/g z: Extra (for improving cycle life) 100% <--buffer y: Irreversible capacity of carbon additive 200 mAh/g h: Capacityof electrode 206.8512 mAh d: (a1 * g1 * x1 + a2 * g2 * x2 + . . . an *gn * xn + c * y + h * z)/b d = 0.06065 g % w = d/(g + d + c + e) = %lithium present in the prelithiated semi-solid anode prior to the appl'nof current % w = 5.718%

TABLE 5 Two Active Material (MGP-A and soft Carbon), 5% Buffer Totalelectrode weight 1 g Active Material 1 = mesophase graphite powder(MGP-A) 25% by volume Active Material 2 = soft carbon 25% by volumeCarbon additive = carbon black 2% by volume Electrolyte 48% by volumeElectrolyte composition ethylene carbonate (EC) 30:00:00 ratio gammabutyrolactone (GBL) 70:00:00 LiBF4 1.1 moles vinylene carbonate (VC) 2%by weight LiBOB 1.5% by weight Tris (2-ethylhexyl) phosphate (TOP) 0.5%by weight Density Active Material 1 = mesophase graphite powder (MGP-A)2.27 g/cc Active Material 2 = soft carbon 2 g/cc Carbon additive =carbon black 1.9 g/cc Electrolyte 1.26 g/cc Active Material 1 =mesophase graphite powder (MGP-A) 33.18% by weight Active Material 2 =soft carbon 29.23% by weight Carbon additive = carbon black 2.22% byweight Electrolyte 35.36% by weight Weight g1: Active Material 1 =mesophase graphite powder (MGP-A) 0.319 g g2: Active Material 2 = softcarbon 0.150 g c: Carbon additive = carbon black 0.022 g e: Electrolyte0.354 g a1: Capacity of Active Material 1 (mesophase graphite): 360mAh/g (<-- @0.1 C) a2: Capacity of Active Material 2 (soft carbon): 391mAh/g (<-- @0.1 C) x1: Estimated % of a1 that is irreversible: 10% x2:Estimated % of a2 that is irreversible: 10% b: Capacity of lithium metal3860 mAh/g z: Extra (for improving cycle life) 5% <-- buffer y:Irreversible capacity of carbon additive 200 mAh/g h: Capacity ofelectrode 156.1 mAh d: (a1 * g1 * x1 + a2 * g2 * x2 + . . . an * gn *xn + c * y + h * z)/b d = 0.00767 g % w = d/(g + d + c + e) = % lithiumpresent in the prelithiated semi-solid anode prior to the application ofcurrent % w = 1.091%  

TABLE 6 Two Active Material (MGP-A and and Silicon), 5% Buffer Totalelectrode weight 1 g Active Material 1 = mesophase graphite powder(MGP-A) 25% by volume Active Material 2 = silicon 25% by volume Carbonadditive = carbon black 2% by volume Electrolyte 48% by volumeElectrolyte composition ethylene carbonate (EC) 30:00:00 ratio gammabutyrolactone (GBL) 70:00:00 LiBF4 1.1 moles vinylene carbonate (VC) 2%by weight LiBOB 1.5% by weight Tris (2-ethylhexyl) phosphate (TOP) 0.5%by weight Density Active Material 1 = mesophase graphite powder (MGP-A)2.27 g/cc Active Material 2 = silicon 2.33 g/cc Carbon additive = carbonblack 1.9 g/cc Electrolyte 1.26 g/cc Active Material 1 = mesophasegraphite powder (MGP-A) 31.65% by weight Active Material 2 = silicon32.49% by weight Carbon additive = carbon black 2.12% by weightElectrolyte 33.73% by weight Weight g1: Active Material 1 = mesophasegraphite powder (MGP-A) 0.317 g g2: Active Material 2 = silicon 0.325 gc: Carbon additive = carbon black 0.021 g e: Electrolyte 0.337 g a1:Capacity of Active Material 1 (mesophase graphite): 360 mAh/g (<-- @0.1C) a2: Capacity of Active Material 2 (silicon): 4200 mAh/g (<-- @0.1 C)x1: Estimated % of a1 that is irreversible: 10% x2: Estimated % of a2that is irreversible: 33% b: Capacity of lithium metal 3860 mAh/g z:Extra (for improving cycle life) 5% <-- buffer y: Irreversible capacityof carbon additive 200 mAh/g h: Capacity of electrode 1016.86 mAh d:(a1 * g1 * x1 + a2 * g2 * x2 + . . . an * gn * xn + c * y + h * z)/b d =0.13389 g % w = d/(g + d + c + e) = % lithium present in theprelithiated semi-solid anode prior to the application of current % w =16.550%

While various embodiments of the system, methods and devices have beendescribed above, it should be understood that they have been presentedby way of example only, and not limitation. Where methods and stepsdescribed above indicate certain events occurring in certain order,those of ordinary skill in the art having the benefit of this disclosurewould recognize that the ordering of certain steps may be modified andsuch modification are in accordance with the variations of theinvention. Additionally, certain of the steps may be performedconcurrently in a parallel process when possible, as well as performedsequentially as described above. The embodiments have been particularlyshown and described, but it will be understood that various changes inform and details may be made.

1. A semi-solid electrode, comprising: about 20% to about 90% by volumeof an active material; 0% to about 25% by volume of a conductivematerial; about 10% to about 70% by volume of a liquid electrolyte; andlithium in an amount sufficient to substantially pre-lithiate the activematerial, wherein the lithium comprises at least one of lithium metal, alithium-containing material and/or a lithium metal equivalent.
 2. Thesemi-solid electrode of claim 1, wherein the lithium amount issufficient to form a solid-electrolyte interface (SEI) layer on asurface of the active material prior to an initial charging cycle of anelectrochemical cell that includes the semi-solid electrode.
 3. Thesemi-solid electrode of claim 1, wherein the lithium includes at leastone of lithium metal powder, lithium salt, lithium foil, and lithiummetal deposited on a current collector.
 4. The semi-solid electrode ofclaim 1, wherein the semi-solid electrode is an anode.
 5. The semi-solidelectrode of claim 1, having a thickness of greater than about 250microns.
 6. The semi-solid electrode of claim 4, wherein the activematerial is graphite.
 7. The semi-solid electrode of claim 6, whereinthe lithium constitutes about 1% to about 12% by volume thereof.
 8. Thesemi-solid electrode of claim 4, wherein the semi-solid anode furthercomprises about 1% to about 50% by volume of a high capacity material.9. The semi-solid electrode of claim 8, wherein the high capacitymaterial includes at least one of tin, silicon, antimony, aluminum,titanium oxide, and/or an oxide or alloy of tin, silicon, antimony, oraluminum.
 10. The semi-solid electrode of claim 8, configured such thatthe lithium intercalates with the high capacity material, theintercalation expanding the semi-solid anode before an initial chargingcycle of an electrochemical cell.
 11. A method of preparing apre-lithiated semi-solid anode, comprising: combining an active materialand a lithium metal or lithium-containing material to form apre-lithiated anode material; combining an electrolyte with thepre-lithiated anode material to form a semi-solid anode material, andforming the semi-solid anode material into a semi-solid anode.
 12. Themethod of claim 11, further comprising: combining a conductive materialwith the pre-lithiated anode material.
 13. The method of claim 11,further comprising: combining a high capacity material with thepre-lithiated anode material.
 14. A method of manufacturing an anode,the method comprising: preparing an anode mixture comprising an activematerial, a conductive material, an electrolyte, and a lithium metaland/or lithium-containing material; and storing the anode mixture in adry environment for a duration sufficient to substantially pre-lithiatethe anode mixture prior to its incorporation into an electrochemicalcell.
 15. The method of claim 14, wherein the storage duration issufficient to form a solid-electrolyte interface (SEI) layer onsubstantially all of the surface area of the active material.
 16. Themethod of claim 14, wherein the active material constitutes between 20%and 90% of the anode mixture.
 17. The method of claim 14, wherein theliquid electrolyte constitutes between 10% and 70% of the anode mixture.18. The method of claim 14, wherein the anode mixture further comprisesa high capacity material.
 19. A method of manufacturing anelectrochemical cell, the method comprising: assembling a cell stack,the assembling including: preparing an anode mixture comprising anactive material, a conductive material, and an electrolyte; applying theanode mixture onto a lithium-bearing substrate; placing a separatormembrane atop the anode mixture; and placing a cathode atop theseparator membrane; and storing the cell stack in a dry environment fora duration sufficient to substantially pre-lithiate the anode mixtureprior to cycling.
 20. The method of claim 19, wherein the storageduration is sufficient to form a solid-electrolyte interface (SEI) layeron substantially all of the surface area of the active material.
 21. Themethod of claim 19, wherein the active material constitutes between 20%and 90% of the anode mixture.
 22. The method of claim 19, wherein theanode mixture further comprises a high capacity material.
 23. The methodof claim 19, the assembling further including: preparing a cathodemixture comprising: a further active material; a further conductivematerial; a further electrolyte; and lithium in an amount sufficient toincrease the stability of the cathode, and forming the cathode from thecathode mixture.
 24. A battery cell comprising the semi-solid electrodeaccording to claim
 5. 25. The battery cell according to claim 23,wherein the semi-solid electrode is an anode, the battery cell furthercomprising a semi-solid cathode having a thickness of greater than about250 microns.